As it stands, if you should die, all your intellectual property is in a state of limbo for 75 years. So no one can use or improve upon that Visual Basic application you’ve been working on, benefit from your essays or record your sheet music.
When a work is in the “public domain”, it is not owned or controlled by anyone. It frees any potential user of your work from having to gain the rights to use it, for any purpose. It can be thought of as the opposite of copyright.